Process of refining oxalic acid



D. E. KELEN.

PROCESS OF REFINING OXALIC ACID.

APPLICATION HLED OCT. 22'; I917.

1 ,39 7 1 27 Patented Nov. 15, 1921.

wow/iioz 8% $3) (jg attozme-tg P QMMMA l UNITED STATES PATENT OFFICE.

DEZSO E. KELEILOF BALTIMORE, MARYLAND, ASSIGNOR TO U. S. INDUSTRIAL ALCOHOL (30., A CORPORATION 03 WEST VIRGINIA.

Specification. of Letters Patent.

Patented Nov. 15,1921.

Application filed October 22, 1917. Serial No. 197,848.

To all w hom it may concern:

Be it known that I, Dnzso E. KELEN, of Baltimore, in the State of Maryland, have invented a certain new and useful Improvement in Processes of Refining Oxalic Acid, and do hereby declare that the following is a full, clear, and exact description thereof.

My invention relates particularly to a process of refining oxalic acid, and is applicable to the refining of the same no matter from what source it has been obtained, although it is applicable especially to the refining of oxalic acid obtained in accordance with the process set forth in the application of Arthur A. Backhaus and Carl Haner, Jr., upon process of treating distillery Waste, Serial Number 203,551, filed November 22, 1917.

The object of my invention is to provide an advantageous method whereby crude oxalic acid may be refined.

A further object is to provide a' process of this character which may be carried out in a simple and inexpensive manner and without requiring any great amount of labor.

A further object is to bring about a separation of crude oxalic acid from the impurities contained therein by taking advantage of the differences of specific gravity thereof.

Further objects of my invention will appear from the detailed description thereof contained hereinafter.

WVhile my invention is capable of being carried out in many different ways, I shall describe only one way of carrying out the same hereinafter, and, while it is capable of being carried out in connection with many different types of apparatus, I shall describe only one type of apparatus for use in connection with the same in the accompanying drawings, in which- The figure is a front elevation of an apparatus which may be used in connection with myinvention.

In the drawings, I have shown a tilting kettle 1, having a steam jacket 2, adapted to be heated by e, g, a current of steam, which may be supplied by a pipe 3 from c, g, a hollow trunnion 4 at one side of the kettle, and which is shown supported in uprights 5 and 6. On said hollow trunnion .4. there is shown a worm gear 7, adapted to be turned by a worm wheel 8, which may be connected with any suitable operating means such s hand wheel 9. The exhaust steam, together with the condensed water from the kettle 1, may be carried off by a pipe 10, which may lead to a hollow trunnion 11 on the kettle 1 and shown as supported in an upright 12.

As one example of the manner in which my invention may be carried out, I may proceed as follows: crude oxalic acid, such, for example, as that obtained in connection with the process set forth in the application of Arthur A. Backhaus and Carl Haner, Jr., above referred to, and which is a brown, almost black, material containing about 75% of oxalic acid and about 25% of organic coloring matter, as well as calcium sulfuric, free sulfuric acid, moisture, etc, may be dissolved in e, 9, water in the proportion of 100 parts by weight of water and 200 parts by weight of crude oxalic acid, and may then be heated to a tem perature approximating 90 C. in the kettle 1. The insoluble materials which consist chiefly of calcium sulfate, will settle out to a large extent upon standing and may be separated from the liquid by filtration through any suitable filter, or by decantation, as by tilting the kettle 1. The clear solution, containing oxalic acid and organic coloring matter, may then be transferred to another tilting kettle of the same type and cooled to 40 to 50 C. During the cooling, the oxalic acid crystallizes out in such a way as to incorporate only a part of the coloring matter in the individual crystals, but the bulk of the coloring matter is precipitated separately. The contents of the kettle are then agitated in any suitable manner, and, owing to the difference in the specific gravity of the oxalic acid crystals and the organic coloring matter, the former settles out at the bottom of the liquid, while the latter remains suspended therein. The kettle may be then tilted to decant the liquid containing the suspended organic coloring matter, and the decanted liquidmay be passed through a filter to separate out the precipitated organic coloring matter from the solution, after which the solution may be returned to the oxalic acid crystals for further agitation withthe oxalic acid crystals and remaining precipitated coloring matter to bring about a separation of a further quantity of the coloring matter from the crystals in the same manner as described above. The crystals of oxalic acid thus obtained are more or less brown in color, due to the organic coloring matter incorporated therewith. These crystals are preferably again dissolved in Water or in a quantity of the mother liquor obtained from previous crystallizations of the oxalic acid in one of the tilting kettles, in the proportion of 100 parts by weight of Water to from 300 to 350 parts by Weight of oxalic acid, by the application of heat until the crystals dissolve. The liquid is then cooled, so as to allow the oxalic acid to crystallize, and it will be found that substantially all the remaining organic coloring matter will be in solution, and may be removed by decantation. In case the decanted liquid contains any insoluble materials, these may be separated from the liquid by filtration, and

the liquid may be returned for further treatment to recover the oxalic acid therefrom in the manner previously described. In order to obtain pure White oxalic acid crystals, the oxalic acid crystals Which have been obtained as above described may be again dissolved in Water or a quantity of the mother liquor andthe operation repeated.

If desired, the oxalic cid crystals may be dissolved in Water or some other solvent and filt red through a charcoal filter. If desired, also, this filtration through the charcoal filter may be carried out Without having subjected the oxalic acid crystals to the last recrystallization previously referred to. The filtration, through the charcoal filter will be found to give the crystals a luster Which they Would not otherwise have. While have described my invention above in detail, I Wish it to be understood that many changes may be made therein Without departing from the spirit of my invention.

I claim:

1. The process of refining crude oxalic acid comprising dissolving it in about onehalf its Weight of Water, bringing it to near the boiling point, filtering off and removing insolubles, crystallizing the acid, agitating the liquid to separate the crystals from organic and suspended matter present, and removing the latter.

2. The process of refining crude oxalic acid comprising dissolving it in about onehalf its Weightin Water, bringing to near the boiling point, removing the insolubles, crystallizing the acid, agitating the liquid to separate the crystals from suspended matter present, decanting the latter, IQ-CllSSOlV- ing the crystals and purifyingthrough an absorbent of coloring matter, and reecrystale lizing the acid.

3.,The process of refining crude oxalic acid comprising dissolving it in water and heating the solution, filtering off and removing insolubles present, crystallizing the acid, agitating the liquid to separate the crystals from organic and suspended matter present ivherebythe latter are kept suspended in the upper part of the liquid, and

removing the organic and suspendedmatter.

Tntestimony that I claim the foregoing I have hereunto set my hand.

DEZso E. KELEN.

Witnesses: V

CARL HANER, J12, ARTHUR A. BACKHAUS. 

